<ion-slides pager >
  <ion-slide >
    <img src="assets/imgs/01.jpg" />
  </ion-slide>
  <ion-slide>
    <img src="assets/imgs/02.jpg" />
  </ion-slide>
  <ion-slide >
    <img src="assets/imgs/03.jpg" />
    <button (click)="slideHasChanged()"> 开始挑战</button>
  </ion-slide>
</ion-slides>
